Presence of Listeria monocytogenes in foods may cause abortions, meningitis

The results of the research conducted in the ICAS Culiacán reveal that at least 10 percent of the fresh cheese, sausages and meats sold in markets and on the street may be contaminated.

Researchers at the Center for Food Research and Development (ICAS) confirmed the presence of Listeria monocytogenes in foods of animal origin, in the city of Culiacan, Sinaloa. The organism causing mainly diarrheal infections as a first symptom, but in more aggressive situations generates abortions and meningitis.

Because in Mexico there are no reports of cases of listeriosis by the health system, the ICAS science team, headed by Christopher Quiroz Chaidez, began working on the search for bacteria. "The only reference is a review from 1982 to 2006, a period in which only 14 cases were reported but not diagnosed because they do not associate diarrheas, abortions or meningitis with Listeria monocytogenes, "says the researcher.

Recent international reports relate the emergence of a strong outbreak of listeriosis in the United States due to consumption of Chinese melon from Mexico.

However, research in different markets were visited for sampling dairy products, sausages and meats, which are taken to the laboratory for analysis by culture media and molecular methods.

After the tests, the five serotypes of Listeria monocytogenes, mainly 4B, which is the most aggressive were found. "We found it in greater amounts in the chicken, with a percentage of 23 percent; sausages by 11 percent; cheeses with nine percent and eight percent meat, "says Quiroz Chaidez.

Therefore, these results suggest that "at least 10 percent of the fresh cheese, sausages and meats sold in markets and on the street may be contaminated with the bacteria."

Human listeriosis is a disease with a high mortality rate (20 to 30 percent) leading to severe diseases such as meningitis, septicemia, and abortions. It usually affects immunocompromised individuals, pregnant women, elderly and children.

While the infection is spread by fecal-oral route of animal to human and from mother to fetus, the main source of infection is by eating contaminated food because of poor hygiene practices. "Upon entering the body, the bacteria travels through the bloodstream, making it easy to reach the meninges, in addition to having the ability to cross the placenta and harm the unborn product," warns Quiroz Chaidez.

The implementation of a preventive programs is required, define the legal framework to ensure food safety, and enforce the reporting of outbreaks. In the latter case, the participation of the health sector is of great importance, since the presence of clinical symptoms suggesting the involvement of bacteria, such as diarrhea, must apply for the necessary studies leading to confirm or exclude the diagnosis.